The effect of the addition of polypropylene-grafted SiO2 nanoparticle on the thermal conductivity of isotactic polypropylene

Abstract

The thermal conductivity of Isotactic polypropylene (iPP)/silica particle (SiO2, 26 nm) nanocomposite has been investigated. The untreated SiO2 and iPP grafted onto SiO2 were dispersed in the iPP (Mw = 2.5 × 105) matrix. The molecular mass of the iPP-grafted chain, Mn, was precisely controlled to be 5.8 × 103, 1.2 × 104, and 4.6 × 104. It was found that the thermal conductivities of graft-treated nanocomposites were higher than that of untreated SiO2 composites. This implied that it is possible to achieve even higher thermal conductivity using the graft treatment. A thermal conductivity analysis conducted using a three-phase model, with considerations for thermal conductivity at interfacial layers, showed that the thermal conductivity of the interfacial layer increased significantly when a graft chain was incorporated. Moreover, the thermal conductivity per graft chain was proportional to the 1/2 power of the molecular mass (\( M_{\text{n}}^{0.5} \)). The results strongly suggest that the thermal conductivity pathway of interfacial layer was the main chain direction of iPP-grafted molecular chains.